@article{MZ_1993__214_1_174590,
     author = {Shun-Cheng Chang},
     title = {Critical {Riemannian} 4-manifolds.},
     journal = {Mathematische Zeitschrift},
     pages = {601--626},
     publisher = {mathdoc},
     volume = {214},
     number = {1},
     year = {1993},
     zbl = {0801.53030},
     url = {http://geodesic.mathdoc.fr/item/MZ_1993__214_1_174590/}
}